The present invention relates to an ultraviolet (UV) irradiation apparatus which may be used in a process for manufacturing a semiconductor device, and more particularly, to a UV irradiation apparatus adapted to facilitate detaching a protective tape from the front side of a back-ground wafer.
In general, a semiconductor device is manufactured on a wafer which is subject to many processes. Good products are selected out of the manufactured semiconductor device by measuring their electrical characteristics, and the selected semiconductor devices are then packaged. In the present process, the wafer is formed to be thin and results in at least one semiconductor device which has been processed to be thin. A method of back-grinding a wafer is widely used as a means to thin the wafer for the semiconductor device after the process of manufacturing it is completed. The process of back-grinding is performed by the steps of: attaching a protection tape to the front side of the wafer in order to protect the semiconductor device; thinning the wafer by back-grinding while the protection tape is attached, by back-grinding; and eliminating the protection tape attached to the front side of the back-ground wafer. In the subsequent process step to eliminate the protective tape backing, a UV irradiation apparatus is widely used. The protective backing has an adhesive coated on one side of the protection tape to cause the tape to adhere to the wafer, and this adhesive coating can be caused to lose its adhesive property via a chemical reaction when exposed to UV. Accordingly, the wafer with the protective tape adhered thereon is usually transferred to the UV irradiation apparatus in order that the upper portion of the tape can be irradiated. Therefore, the UV rays cause the adhesive property to be lost so that the protection tape can be removed from the wafer. Such chemical reaction of the adhesive is affected by both the temperature and the distribution of the UV irradiation on the adhesive.
The conventional UV irradiation apparatus consists of a UV lamp for generating UV rays which is fixed in a chamber, a wafer transferor installed under the UV lamp for transferring the wafer, and a reflector adapted to surround the UV lamp in order to concentrate UV on the wafer and wafer transferor. In such a process step, a vacuum chuck or a roller is widely used as the wafer transferor.
In general, the transferring method is by a vacuum chuck which rotates and at the same time, horizontally transfers the wafer lying thereon to the UV irradiation apparatus, or only horizontally transfers it. In such a process, when the vacuum chuck rotates the wafer, the wafer thereon is rotated on its center axis. Accordingly, this results in the central portion of the wafer being concentratedly irradiated with more UV rays than that of the peripheral portion thereof. Likewise in the wafer transfer method which utilizes a roller, the wafer is horizontally moved according to a rotating movement of a plurality of rollers upon which the wafer lies. A desired uniform smooth transfer movement is difficult to obtain in such a process. Since each of the rollers can neither rotate at a uniform speed nor transfer a uniform force to the wafer, a smooth movement of the wafer is prevented. As the result it is difficult to automate such a step without jamming occurring, which presents manufacturing problems. If a successive wafer is prevented from proceeding to or from the UV irradiation apparatus, it results in a halt to the desired UV irradiation process step which cannot be performed. Another difficulty in the irradiation process is caused by the UV lamp, which usually generates not only the desired UV rays but also undesired infrared and visible rays. Thus, the wafer is also irradiated with the undesired infrared rays and visible rays. This usually leads to an increase in the temperature of the wafer and thereby causing the wafer to suddenly cool down to room temperature after completing the UV irradiation. Thus, the undesired quick-cooling problem prevents the adhesive from completely losing its adhesive property before cooling.
In the conventional UV irradiation apparatus, the UV lamp is fixed in a chamber so that it is impossible to freely control a distance between the UV lamp and a wafer. Accordingly, since the amount of UV irradiated on the wafer cannot be appropriately controlled, it is difficult to maximize a chemical reaction within the adhesive to cause it to release the wafer. The temperature around the wafer is a result of the heat generated only by the UV lamp and it is difficult to freely provide an optimum temperature where the adhesive can lose its adhesive property.
As pointed out above, in the conventional UV irradiation apparatus where a wafer is transferred by rollers, the horizontal movement of wafer is not smooth. Therefore, when the wafer after UV irradiation is loaded on a carrier, the wafer can be damaged or broken due to colliding with the carrier.
By the conventional UV irradiation apparatus as described above, the whole surface of the wafer cannot be uniformly irradiated with UV rays, which makes it difficult to freely control the quantity of UV irradiation on the wafer and the temperature of the wafer. The temperature of the wafer can be also increased by the UV irradiation apparatus lamp. Such a UV lamp also results in irradiation of infrared rays which generate heat, and further the heated wafer suddenly cools to a room temperature after that the UV irradiation on the adhesive on the wafer surface sometimes does not lose its adhesive property. In such a case, it is difficult to easily eliminate the protective tape from the wafer surface.